1. Field of the Invention
This invention relates to high temperature industrial roof structures, particularly to tin bath roof structures as are used in furnaces for the production of sheet glass. The roof structure of this invention uses hanger bricks which may be hung by metallic hangers from a support structure with a metallic hanger attachable on the hanger brick permitting design to a wide variety of roof widths and oversize hanger bricks and filler bricks to be cut on the job site for adjustment to exact roof widths. The roof structure of this invention may be constructed to a wide variety of dimensions using a single style of hanger brick and a single style of filler brick.
2. Description of Prior Art
High temperature industrial furnaces require interior structures of heatresistant refractory bricks or tiles. Such interior structures are heavy and require support from a substantial support frame which is constructed of structural steel. The roof support frame is usually constructed of large I-beams or wide flange beams with rods suspending metallic hangers from which hanger bricks are suspended. Spaced rows of hanger bricks are suspended from the roof support frame and rows of filler bricks are placed in the space between adjacent rows of hanger bricks and supported on the opposite sides by the adjacent hanger bricks. Hanger bricks typically used for tin bath roofs are shaped so that a hanger may be placed only at the end of the hanger brick. Conventionally, a single metallic hanger supports the ends of two adjacent end-to-end hanger bricks. Present roof structures frequently require as many as 8 to 12 different styles of hanger bricks and as many as 8 to 12 different styles of filler bricks, necessitating that many different molds with manufacture of that many styles of brick together and supply of that many styles of brick to the job site, to accommodate varying roof dimensions.
One concept which addresses these issues is taught by U.S. Pat. No. 5,357,540. There a hanger brick is disclosed having a flat generally rectangular lower face which is at least about {fraction (2 1/2+L )} times as long as it is wide, which lower face portion of the brick has a filler brick support ledge extending outwardly for the full length of the brick along opposite sides for sufficient height and outward distance to support adjacent filler bricks. A narrower upper hanger portion of the brick has a hanger recess for the full length of the brick along opposite sides to provide bearing for a hanger suspending the hanger brick. The upper hanger portion of the brick, above the hanger recess, has a plurality of spaced generally laterally extending lugs providing a plurality of hanger attachment positions along the hanger portion of this hanger brick. One end of the hanger brick has an extending ridge and the opposite end has a recess sized to accept the corresponding extending ridge on the edge of an adjacent hanger brick. 
Current practice, acceptable for conventional bath roof design, is to have the lower end of the suspension metallic close to the refractory hot-face. However, such a design in a high temperature tin bath application results in exposure of the suspension metallic to extremely high temperaturesxe2x80x94sufficient to cause failure. In addition, current designs limit the amount of insulation which can be used as a result of which a substantial amount of heat loss can occur.
Accordingly, it is one object of this invention to provide a refractory hanger which is designed so as to allow optimum insulation of the roof in high-temperature manufacturing processes while simultaneously protecting the suspension metallics.
This and other objects of this invention are addressed by the use of a refractory hanger brick comprising an elongated upwardly extending refractory portion (also referred to herein as a xe2x80x9cpostxe2x80x9d) having a generally rectangular cross section in a direction transverse to its length and a lower refractory based portion having a generally rectangular lower face. Each side of the base portion has a base length greater than a corresponding side of the elongated upwardly extending refractory portion so as to provide support for insulating material and/or adjacent filler bricks. The upper end of the elongated upwardly extending refractory portion distal from the lower refractory base portion forms a hanger recess on opposite sides thereof. At least one generally laterally extending lug is disposed above each hanger recess to retain the hanger in a fixed position and to provide at least one hanger position along the opposite sides of the upper end of the elongated upwardly extending refractory portion of the refractory hanger brick.
In accordance with one embodiment, one substantially vertical face of the lower refractory base portion comprises a ridge disposed generally parallel to the lower face and an opposite substantially vertical face of the lower refractory base portion forms a recess sized to mate with the ridge of an adjacent hanger brick. In accordance with another embodiment of this invention, a refractory knob or key extending outwardly from opposite sides of the elongated upwardly extending refractory portion proximate the lower refractory base portion is provided for mating with corresponding recesses in the sides of refractory xe2x80x9crailxe2x80x9d bricks interposed between adjacent refractory hanger bricks.
Filler bricks used in high temperature furnace roof structures of this invention have a flat generally rectangular lower face which is generally wider in width than a refractory hanger brick. The length of the filler brick is not critical, but is typically less than the length of the hanger brick so that the end joints do not match. The filler bricks have generally flat end faces and the lower portion on opposite sides has a recess to match the outwardly extending filler brick support ledge, by which a row of filler bricks is supported on opposite sides between rows of hanger bricks. This design of filler brick allows each filler brick to be removed by lifting upwardly. The roof design of this invention considerably reduces joint lengths in the furnace roof, since presently used filler bricks are about the same width as the hanger bricks, and increases accessability to the cold side of the bricks for repair and placement, since considerably fewer hanger bricks are required for a given area.
Similarly, refractory xe2x80x9crailxe2x80x9d bricks used in high temperature furnace roof structures of this invention have a flat generally rectangular lower face which in width is wider than the width of a refractory hanger brick. The length of the refractory rail brick is not critical, but is generally less than the length of the corresponding side of the refractory hanger brick on which the refractory rail brick is disposed. Like the filler bricks, the refractory rail bricks have generally flat end faces and the lower face portion on opposite sides has a recess to match the outwardly extending support ledge of the refractory hanger bricks by which a row of refractory rail bricks are supported on opposite sides between rows of refractory hanger bricks. A portion of the opposite sides above the recesses formed by the refractory rail brick forms a key recess which mates with the refractory knob or key on the refractory hanger brick so as to provide a guide for locating the refractory rail bricks between adjacent rows of the refractory hanger bricks. As in the case of the filler bricks, this design of refractory rail bricks allows each rail brick to be removed by lifting upwardly.
Sub-assemblies, or bays, along the length of the furnace may be made a variety of lengths using the refractory hanger brick, refractory filler brick and refractory rail brick of this invention. The width of the bricks may be made in metric dimensions to accommodate metric dimensions for the furnace length. Likewise, the roof structure of this invention may be readily designed to various roof dimensions by use of shorter end bricks which may continue to be supported by hangers in the same fashion as the rest of the roof.
Electrically heated tin bath furnace roofs of this invention have electrical bus bars which extend lengthwise of the roof and are fed through the top of the furnace casing requiring less length wire leads and avoiding obstructions at the side of the furnace, as compared to present tin bath roofs in which electrical bus bars generally extend across the width of the roof and are fed through the side or top of the furnace casing.